Photographic fine grain silver halide emulsions

ABSTRACT

A PROCESS OR PREPARING FINE-GRAIN LIGHT-SENSITIVE SILVER HALIDE EMULSIONS OF THE LIPPMANN TYPE IS DESCRIBED WHEREIN PRECIPITATION OF THE SILVER HALIDE GRAINS OCCURS IN THE PRESENCE OF A COMPOUND OF THE FORMULA:   Z-A-X   WHEREIN EACH OF Z AND X STANDS FOR A HETEROCYCLE COMPRISING THE MOIETY=N-AND A REPRESENTS A CHEMICAL BOND ALKYLENE, ALKYLENE INTERRUPTED BY OXYGEN OR -N (R)-, R BEING HYDROGEN OR C1-C4 ALKYL, ARYLENE, ALKENYLENE OR~S-ALKYLENE-S~OR~S-ALKYLENE~THE ALKYLENE GROUPS OF WHICH MAY BE INTERRUPTED BY OXYGEN OR THE GROUP -N(R)-. THE AVERAGE SILVER HALIDE GRAIN SIZE CAN BE REDUCED TO LESS THAN 50 NM. THE EMULSIONS SHOW A HIGH DIFFRACTION EFFICIENCY AND A HIGH SIGNAL TO NOISE RATIO.

United States Patent Ofice Patented Nov. 28, 1972 3,704,130 PHOTOGRAPHIC FINE GRAIN SILVER HALIDE EMULSIONS Robert Joseph Pollet, Vremde, Herman Adelbert Philippaerts, Mortsel, Jozef Frans Willems, Wilrijk, and Frans Henri Claes, Edegem, Belgium, assignors to Gevaert- Agfa N.V., Mortsel, Belgium No Drawing. Filed Oct. 2, 1970, Ser. No. 77,695 Claims priority, application Great Britain, Oct. 29, 1969, 53,025/69 Int. Cl. G03c 1/02 US. Cl. 96114.7 14 Claims ABSTRACT OF THE DISCLOSURE A process of preparing fine-grain light-sensitive silver halide emulsions of the Lippmann type is described wherein precipitation of the silver halide grains occurs in the presence of a compound of the formula:

wherein each of Z and X stands for a heterocycle comprising the moiety =N and A represents a chemical bond, alkylene, alkylene interrupted by oxygen or N(R), R being hydrogen or C C alkyl, arylene, alkenylene or S-alkylene-S- or S-alkylenethe alkylene groups of which may be interrupted by oxygen or the group N(R). The average silver halide grain size can be reduced to less than 50 nm. The emulsions show a high diffraction efiiciency and a high signal to noise ratio.

The present invention relates to the preparation of lightsensitive silver halide emulsions; more particularly to the preparation of fine-grain silver halide emulsions of the Lippmann type; to the fine-grain silver halide emulsions prepared according to this method, and to photographic elements having at least one layer of the aforesaid finegrain silver halide emulsion.

Lippmann-emulsions, normally having an average grainsize of about 50100 nm., are of particular importance for the preparation of photographic plates or films with high resolution; for use in microphotography and in astrophotography; for recording nucleo-physical phenomenons; for the preparation of masks in the production of microelectronic integrated circuits; for use in holography, etc.

Nowadays there is an increasing demand for photographic plates or films having Lippmann-emulsion layers, the average grain-size of which is less than 50 nm. These materials are of particular importance for reflection-holograms where a high difi'raction efliciency and a high signal to noise ratio are required.

Attempts to prepare Lippman-emulsions with an average grain size smaller than usual i.e. smaller than 50 nm. by varying the working conditions during the precipitation of the silver halide, have not been successful and therefore, it has been tried to use compounds restraining the growth of the silver halide crystals during precipitation.

It has now been found that silver halide emulsions with very fine grain can be prepared by efiecting the precipitation of the silver halide in an aqueous hydrophilic colloid medium in the presence of compounds corresponding to the following general formula:

ZAX wherein each of Z and X (the same or different) stands for a heterocycle including a substituted heterocycle and a heterocycle with fused-on ring, said heterocycle comprising the moiety =N e.g. imidazole, benzimidazole, naphthimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, thiazole, benzothiazole, etc., and

A stands for a chemical bond, alkylene for example methylene, ethylene, tetramethylene, etc. including alkylene interrupted by oxygen or N(R) wherein R=hydrogen or alkyl comprising at most 4 C-atoms, arylene, alkenylene, such as vinylene and S-al-kylene- S or S-alkylenethe alkylene groups of which can be interrupted by oxygen or N(R) wherein R has the same significance as above.

The compounds corresponding to the above general formula are bidentate ligands which form complexes or salts with silver, thus restraining growth of the silver halide crystals so that very fine silver halide grains are formed.

By the use of compounds corresponding to the above general formula during the precipitation step of the silver halide, homogeneous Lippmann-emulsions can be prepared with an average grain size markedly smaller than in the absence of said compounds so that emulsions are obtained practically without scattering.

The compounds or solutions of these compounds of use according to the present invention are generally added into the aqueous hydrophilic colloid composition, more particularly aqueous gelatin, into which the silver halide is precipitated. They can be used in amounts varying between very wide limits, preferably between 2 g. and 20 g. per mole of silver halide.

The ratio of hydrophilic colloid binder to silver halide in the fine-grain emulsions according to the present invention is preferably comprised between 0.2 and 6.0.

The hydrophilic colloid used as the vehicle for the silver halide may be any of the common hydrophilic colloids employed in photographic light-sensitive emulsions, for example gelatin, albumin, zein, casein, algininc acid, collodion, a cellulose derivative such as carboxymethyl cellulose, a synthetic hydrophilic colloid such as polyvinyl alcohol and poly-N-vinyl pyrrolidone, etc. gelatin being however preferred. If desired compatible mixtures of two or more colloids may be employed for dispersing the silver halide.

Various silver salts may be used as the light-sensitive salt such as silver bromide, silver chloride or mixed silver halides such as silver chlorobrmide, silver bromoiodide and silver chlorobromoiodide. Emulsions containing silver bromide or silver chloride or a mixture of silver chloride and silver bromide and such emulsions containing small amount of silver iodide up to 8% are favoured.

After precipitation of the silver halide grains in the presesce of the compounds of use according to the present invention the emulsion is washed in order to remove the water-soluble salts whereupon the emulsions may be chemically as well as spectrally sensitized.

They may be spectrally sensitized by any of the known spectral sensitizers such as cyanines and merocyanines for photographic silver halide materials. They may be chemically sensitized by means of sulphur compounds for example allyl thiocyanate, allyl thiourea, sodium thiosulphate, etc. They may also be sensitized by means of reductors for instance tin compounds, imino-amino methane sulphinic acids and derivatives thereof, cadmium salts, and small amounts of noble metal compounds such as gold, platinum, palladium, iridium, ruthenium and rhodium. The emulsions according to the invention may also comprise compounds which sensitize the emulsion by development acceleration for example quaternary ammonium compounds and compounds of the polyoxyalkylene type.

Further, the emulsions may comprise antifoggants and stabilizers for example heterocyclic nitrogen-containing thioxo compounds such as benzothiazoline-Z-thione and 1- phenyl2-tetrazoline-5-thione, compounds of the hydroxytriazolopyrimidine type such as 5-methyl-7-hydroxy-striazolo[1,5-a1pyrimidine and mercury compounds.

Any of the hardening agents for hydrophilic colloids may be used in the emulsions according to the present invention for example formaldehyde, dialdehydes, diketones, halogen substituted aldehyde acids such as mucochloric acid and mucobromic acid, etc.

4 solution of gelatin. The conditions of precipitation were adjusted so that a Lippmann emulsion with an average grain size of 67 mm. was obtained. Details as to the preparation of Lippmann-emulsions can be found amongst others in P. Glafkides, Photographic Chemistry, v01. 1,

The emulsions may be coated on a wide variety of 1958, Fountain Press, London. i photographic emulsion supports. Typical supports include Um'ier completely analogous wofkmg Condlfions other cellulose ester film, polyvinyl acetal film, polystyrene fil emulsions were prepared wlth the d fference that the IQ% Polyethylene terephthalate fil and l d fil f i aqueous solution of gelatin into WhlCh the silver bromlde ous m t rial a ell as paper nd l 10 was precipitated now contained one of the compounds The following example illustrates the present invention. listed in the table below in an amount of P 111016 of silver nitrate used. EXAMPLE The average silver bromide grain size was determined A silver bromide emulsion comprising 25 g. of silver by turbimetry. bromide and 65 g. of gelatin was prepared by simultaneous 15 The results attained are listed in the table below and addition of an aqueous silver nitrate solution and an show that the compounds corresponding to the above aqueous potassium bromide solution to a 10% aqueous general formula restrain growth of the silver halide grains.

"Average gramstze No. Compound added in nm.

Nona 67 l N=C I 46.5 HOaS-(CHzh-S-T Ts-wum-soazr 1' N--- OHz-CHz- -N 1 (I:H3 1 HaCC-CHr-(|JS(['|J Ifil I? (flJ-S-(f-CHa-C-Cfla S OaNa H NCCHr-CHzC--N H S OaNa a H H 47.5

(")SCHzCHrSC -N N N I 7H3: E g 37 Ts-cm-sT NflOzS -N J S OJNS I -s-on /N I Average gralnsize No. Compoundadded tnnm.

CH2(CH2)r-CHzC H018 LL ILL S;H

I if Q (")CHrCH2- The compounds used in the above example can be prepared as described in the following preparations.

Preparation lzcompound 1 22.5 g. (0.142 mole) of 1,2-diaminonaphthalene and 17.5 g., (0.142 mole) of isonicotinic acid were heated for 8 hours at 160 C. in 50 g. of polyphosphoric acid. After having been cooled the reaction mixture was boiled with 600 ml. of water and 200 ml. of hydrochloric acid, filtered over decolourizing carbon, cooled to room-temperature and added dropwise to 300 ml. of ammonium hydroxide at C. The precipitate formed was recrystallized from a mixture of 210 ml. of ethanol and 490 ml. of acetonitrile.

Melting point: 250 C.

Yield: 18 g.

Preparation 2 compound 2 To a solution of 11.4 g. of 1,2-bis(5-mercapt0-1H-1,2,- 4-triazol-3-yl)ethane prepared as described in Bull. Soc. Chim. Belg. 75, 358 (1966) and 12 g. of sodium methylate in 150 ml. of methanol, 18 g. of propane sultone were added. The mixture was refluxed for 3 hours and then filtered over decolourizing carbon. The filtrate was concentrated by evaporation and the residue was dissolved in ethanol. The product was precipitated by means of acetone.

Yield: 22 g.

Preparation 3 :compound 3 To a solution of 11.4 g. of 1,2-bis(5-mercapto-1H-1,2,- 4-triazol-3-yl) ethane and 12 g. of sodium methylate in 150 ml. of methanol, g. of 1,1,3-trimethylpropanesultone were added. The mixture was refluxed for 3 hours and filtered over decolourizing carbon. The filtrate was concentrated by evaporation and the residue dissolved in ethanol. The product was precipitated by means of acetone.

Yield: 30 g.

Preparation 4zcompound 4 This compound was prepared as described in J]. Org. Chem. 24, 1462 (1959).

Preparation 5zcompound 5 To 15 g. (0.1 mole) of Z-mercapto-benzimidazole a solution of 5.4 g. (0.1 mole) of sodium methylate in 150 ml. of methanol and 8.35 g. (0.05 mole) of 1,2-dibromoethane were added. The reaction mixture was refluxed for 3 hours and then concentrated by evaporation. The residue was recrystallized from a mixture of 150 ml. of ethanol and 50 ml. of water.

Melting point: 235" C. Yield: 4 g.

Preparation 6zcompound 6 24.6 g. (0.2 mole) of a-picolinic acid and 21.6 g. (0.2 mole) of o-phenylenediamine were heated to 250 C. in 20 minutes and kept at this temperature for 20 minutes, the water formed being removed by distillation. The residue was dissolved by heating in m1. of hydrochloric acid 5 N whereupon it was precipitated again by means of ammonium hydroxide. The precipitate was filtered by suction and recrystallised from a mixture of 200 ml. of ethanol and 100 ml. of water.

Melting point: 224' C.

Yield: 17.5 g.

Preparation 7 :compound 7 To a solution of 27.5 g. (0.1 mole) of the disodium salt of 2-mercapto-5(6) sulphobenzimidazole in 200 ml. of dimethylformamide 8.7 g. (0.05 mole) of dibromomethane were added dropwise with stirring at room-temperature. The solution was heated for 3 hours at 100 C. whereupon it was concentrated by evaporation and the residue recrystallized from a mixture of 300 ml. ethanol and 40 ml. of water.

Yield: 8 g.

Preparation 8zcompound 8 43 g. (0.4 mole) of o-phenylenediamine and 33.5 g. (0.2 mole) of 2,6-pyridinedicarboxylic acid were heated in 40 g. of polyphosphoric acid for 6 hours at C. After having been cooled the reaction mixture was poured into 400 ml. of water and the precipitate formed was filtered by suction and washed till neutral. The product was recrystallized from a mixture of water and ethanol.

Melting point: 250 C. Yield: 36 g.

Preparation 9zcompound 9 To a solution of 27.5 g. (0.1 mole) of the disodium salt of 2-mercapto-5(6)-sulphobenzoimidazole in 200 ml. of dimethylformamide, 12.7 g. (0.1 mole) of 2-chloromethylpyridine were added dropwise at room temperature with stirring. Then the solution was heated at 80 C. for 4 hours. The precipitate of sodium chloride formed was filtered by suction and the filtrate concentrated by evaporation. The residue was taken up with heating in water and extracted with ether whereupon the aqueous layer was acidified with 15 ml. of acetic acid. After having been cooled, the precipitate formed was filtered by suction and dried at 80 C. under reduced pressure.

Yield: 25.6 g.

Preparation lzcompound To a solution of 18 g. (0.06 mole) of 1,4-bis(2-benzimidazolyl) butane in 180 ml. of sulphinic acid were added dropwise 54 g. of fuming sulphuric acid (24% of S0 The reaction mixture was kept between 70 and 80 C. until a sample taken dissolved completely in a solution of sodium carbonate. The reaction mixture was poured into icewater and the precipitate formed was filtered by suction. The white powder formed was purified by dissolving it in sodium carbonate and then precipitating it by means of acetic acid.

Yield: 19 g.

Preparation llzcompound 11 This compound Was prepared as described in II. Prakt. Chem. 34, 64 (1966).

Preparation 12 compound 12 This compound was prepared as described in 11. Gen. Chem. USSR 31, 1586/1961.

Preparation 13 :compound 13 This compound was prepared as described in Ber. 21, 1077 (1888).

We claim:

1. Method of preparing a photographic fine-grain silver halide emulsion which comprises the step of precipitating the silver halide in an aqueous hydrophilic colloid medium in the presence of a compound corresponding to the following general formula:

wherein:

each of Z and X (the same or different) stands for a heterocycle, a substituted heterocycle or a heterocycle with fused-on ring, said heterocycle comprising the moiety =N, and

A stands for a chemical bond, alkylene, alkylene interrupted by oxygen or --N(R) wherein R=hydrogen or alkyl comprising at most 4 C-atoms, arylene, alkenylene, S-al-kylene-S- or s-alkylene, the alkylene groups of which can be interrupted by oxygen or --N(R)-- wherein R has the same significance as above; said compound being present in an amount suflicient to restrain growth of silver halide grains.

2. Method according to claim 1, wherein each of Z and X (the same or different) stands for imidazole, benzoimidazole, naphthoimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, thiazole, or benzothiazole.

3. Method according to claim 1, wherein said compound is present in the aqueous hydrophilic colloid medium into which the silver halide is precipitated in an amount sufiicient to effectively restrain growth of the silver halide grains.

4. Method according to claim 1, wherein the emulsion is a silver bromide, silver chloride or a silver chloro- 8 bromide emulsion which may comprise a minor amount of silver iodide.

5. A photographic fine-grain silver halide emulsion wherein said emulsion is prepared by precipitating the silver halide in an aqueous hydrophilic colloid medium in the presence of a compound corresponding to the following general formula:

ZAX wherein:

each of Z and X (the same or difierent) stands for a heterocycle, a substituted heterocycle or a heterocycle with fused-on ring, said heterocycle comprising the moiety =N, and

A stands for a chemical bond, alkylene, alkylene interrupted by oxygen or -N(-R)- wherein R=hydrogen or alkyl comprising at most 4 C-atoms, arylene, alkenylene, S-alky1ene-S- or S-alkylene, the alkylene groups of which can be interrupted by oxygen or --N(R)- wherein R has the same significance as above; said compound being present in an amount sufiicient to restrain growth of silver halide grains.

6. Method according to claim 2 wherein A is alkylene.

7. Method according to claim 2, wherein A is S- alkylene.

8. Method according to claim 2 wherein A is S- alkylene-S-.

9. Method according to claim 2 wherein A is a chemical bond.

10. Photographic material according to claim 5 wherein Z and X (the same or diflerent) stand for imidazole, benzoimidazole, naphthoimidazole, pyridine, quinoline, pyrazole, tetrazole, triazole, thiazole, or benzothiazole.

11. Photographic material according to claim 10 wherein A is alkylene.

12. Photographic material according to claim 10 wherein A is S-alkylene.

13. Photographic material according to claim 10 wherein A is S-alkylene-S-.

14. Photographic material according to claim 10 wherein A is a chemical bond.

References Cited UNITED STATES PATENTS 3,528,810 9/1970 Weyde 96-94 FOREIGN PATENTS 719,679 10/1965 Canada 96-94 1,051,869 12/1966 Great Britain 96-ll4.7 1,111,492 4/1968 Great Britain 96--114.6

NORMAN G. TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner us. 01. X.R. 9694 

